It is well known that, under selection pressure, viruses often mutate to drug-resistant strains, thereby limiting the efficacy of most antiviral agents. Those viral structures that are required for viability and growth are often good drug targets because their inactivation cannot be easily overcome by mutation. The utility of these targets can be further enhanced if the structures are mutationally intolerant. Furthermore, these structures may be conserved and/or maintained between virus families, groups or genuses.
In particular retroviruses such as HIV, can become rapidly resistant to drugs used to treat the infection due to the high error rate of the reverse transcriptase enzyme responsible for transcribing its RNA genome. HIV is an example of such a hyper-mutable virus. It has diverged into two major species, HIV-1 and HIV-2, each of which has many clades, subtypes and drug resistant variations.
Strategies for coping with emergence of viral drug-resistant strains include combination drug therapies (Lange (1996) AIDS 10 Suppl 1:S27-S30). Drugs against different viral proteins and drugs against multiple sites on the same protein are commonly used as a strategy to overcome the adaptability of the virus. Combination therapies for retroviruses, using, e.g., protease inhibitors and nucleoside analogues, such as AZT, ddI, ddC and d4T, can become ineffectual; the virus develops complete resistance in a relatively short period of time (Birch (1998) AIDS 12:680-681; Roberts (1998) AIDS 12:453-460; Yang (1997) Leukemia 11 Suppl 3:89-92; Demeter (1997) J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. 14(2):136-144; Kuritzkes (1996) AIDS 10 Suppl 5:S27-S31). Furthermore, no effective anti-retroviral vaccine is currently available (Bolognesi (1998) Nature 391:638-639; Bangham (1997) Lancet 350:1617-1621).
The HIV-1 caused AIDS epidemic began about 18 years ago. Since then the number of new cases have increased over time. By the end of 1994, Pat. No. 1,025,073 AIDS cases had been reported to the WHO, with a 20% increase in the number of cases since December, 1993 (Galli (1995) Q. J. Nucl. Med. 39:147-155). By the year 2000, the WHO predicts that there will be 30 to 40 million cumulative HIV-1 infections in the world (Stoneburner (1994) Acta Paediatr. Suppl. 400:1-4).
The Gag and Gag-Pol proteins in the Retroviridae, except for Spumaviruses, contain a highly conserved zinc finger motif (CCHC) within the nucleocapsid p7 (NCp7) protein portion of the polyprotein (see definitions, below). The absolute conservation of the metal chelating cysteine and histidine residues along with other residues of the protein and its in participation in essential functions during early and late virus replication has identified this feature as an antiviral target. Mutations of the chelating residues in the zinc fingers yield a non-infectious virus. Because zinc fingers are identical in most retroviruses, reagents able to inhibit its function have the potential of being broad spectrum anti-viral therapeutic drugs. For example, it has been shown that compounds that target the zinc finger by irreversible binding and cause ejection of the zinc molecule exhibit antiviral activity (see, e.g., U.S. Pat. No. 6,001,555; Rice et al., Nature 361:473-475, 1993). Disulfide benzamidines were also shown to be active in acutely and chronically infected cell lines (Rice et al., Science 270:1194-1197, 1995), and a series of pyridinioalkanoyl thioesters were developed that had superior anti-HIV-1 activity and less toxicity compared to the disulfide benzidines (see, e.g., Turpin et al., J. Med. Chem. 42:67-86, 1999). A cyclic peptide that mimics several binding determinants in NC-p7 and inhibits NC-p7 annealing activities has also been designed (e.g., Druillennec et al., Proc Natl. Acad. Sci USA 96:4886-4891, 1999; Druillennec et al., Bioorg Med Chem Lett 9:627-632, 1999). More recently, a series of tricyclic compounds have been identified that inhibit binding of NC-p7 to a short oligonucleotide, d(TG)4, and that have anti-HIV activity (see, e.g., Stephen et al., Biochem. Biophys. Res. Comm. 296:1228-1237, 2002; and WO 02/062333).
Antimony-containing oxo-metalate complexes have been disclosed that have anti-viral activity (e.g., U.S. Pat. No. 5,041,576), however these compounds are limited to antimony oxo-metalate complexes that have molybdate and tungstate moieties. The present invention now provides new methods of inhibiting viral replication using antimony compounds or diphenyl compounds that disrupt nucleocapsid/nucleic acid binding interactions.